Electric fuse for rocket



April 14, 1964 J. R. JASSE 3,

' ELECTRIC FUSE FcSR ROCKET Filed July 10, 1961 2 Sheets-Sheet 1 April 14, 1964 J. R. JASSE ELECTRIC FUSE FOR ROCKET 2 Sheets-Sheet 2 Filed July 10, 1961 Fig-7 United States Patent 3,128,705 ELECTRIC FUSE FOR ROCKET Joseph Raymond Jasse, Paris, France, assignor to Hotchhiss-llrandt, Paris, France, a corporation of France Filed July 10, 1961, Ser. No. 122,987 Claims priority, application France July 21, 1960 Claims. (Cl. 102-70.2)

The present invention relates to electric base fuses for rockets having a hollow charge and whose operation on impact is ensured by a percussion fuse of known piezoelectric type mounted forward of the hollow charge head and connected to the base fuse by two conductors, this percussion fuse producing on impact an electric current which feeds and causes operation of the base fuse. The primer of the latter, which is located in the vicinity of the hollow charge, permits, by its electric ignition, the ignition of said hollow charge much more rapidly than is possible with a conventional point fuse.

Known electric base-fuses possess numerous disadvantages. They become armed either immediately (sometimes even in the launching tube) or at the end of the operation of the jet propelling means. In the first case, the fuse is liable to operate at a short distance from the launching aircraft which is dangerous for the latter, and if the rocket after having started to move oif becomes wedged in the launching tube and the fuse is already armed, precautions must be taken to withdraw the wedged rocket. In the second case, the distance travelled through by the rocket before the fuse is armed could be too great and could preclude firing on a near target.

The object of the invention is to provide an electric base fuse for a rocket so improved as to avoid the aforementioned disadvantages.

This improved fuse which is absolutely safe before the launching of the rocket and ensures safe operation near the muzzle of the launching tube, is of the type comprising a pivotable support carrying the electric primer and detonator which in the position of rest breaks the pyrotechnic chain between the fuse and the charge to ignite, and the fuse has a body which is composed of an insulating material and carries two fixed terminals and a first electrode of the electrodes of the electric primer carried by the pivotable support is permanently connected to a first terminal of said terminals whereas a second electrode of the primer is connected to a contact element carried by the pivotable support in such manner that said contact element is in cont-act with said first terminal when the support is in the position of rest but in contact with said second terminal when the support is in the armed position.

Further features and advantages of the invention will be apparent from the ensuing description, with reference to the accompanying drawings to which the invention is in no way limited.

In the drawings:

FIG. 1 is a front elevational view of a fuse according to the invention in the position of rest, the cover having been partly broken away.

FIGS. 2 and 3 are sectional views taken roughly along lines 2--2 and 3-3 of FIG. 1.

FIG. 4 is a partial sectional View taken along line 4-4 of FIG. 1.

FIG. 5 is a partial View of the rear face of the fuse showing the electric connection terminals.

FIG. 6 is an elevational view of a sleeve having a zigzag groove of a pneumatic dash-pot which retards the arming of the fuse.

FIG. 7 is a front elevational view of the fuse in the armed position, the cover having been removed.

FIG. 8 is a sectional view taken roughly along line 88 of FIG. 7.

FIGS. 9 and 10 are diagrams of the electric connections before and after arming respectively, and

FIG. 11 is a diagrammatic view of a rocket provided with the fuse according to the invention.

In the illustrated embodiment, the fuse comprises a body A composed of a material which is not conductive of electricity, this body having a base 1 and a cylindrical tube 2. Fixed to the latter is a metal cover 3, this cover being fixed by screws 4 screwed in tapped holes 5 formed in reinforced portions of the tube 2. This cover is provided with a central aperture 6 provided for the passage of the flames of the fuse toward the charge to ignite.

Disposed in the cavity of the body A closed by the cover 3 and pivotable about an axis WW which is parallel with the longitudinal axis X-X of the tube 2 but eccentric relative to the latter is a pivotable support B constituting a primer and detonator carrier and composed of a material which is not conductive of electricity. This support B comprises, moulded therewith, three hollow cylindrical portions 7, 8, 9 which have parallel axes and are interconnected by webs 10, the support having, when viewed from the front end, a shape in the form of an L.

The cylindrical portion 7 is mounted for rotation about the axis W-W on a fixed journal 11 carried by the base 1 of the body A and centered at 12. (FIGS. 3 and 8) in the metal cover 3. The support B is maintained axially in position between a split elastic ring 13 engaged in a recess 14 in the journal 11 and a shoulder 15 on the latter. The support B is biased to turn about the axis W-W in the direction of arrow f (FIG. 1) from the unarmed position of rest shown in FIGS. 1 to 3 to the armed position shown in FIGS. 7 and 8, by the action of a spring 16 (FIG. 3) whose ends are fixed in the pivotable support and the journaled respectively.

The second cylindrical portion 7 (FIG. 2) is so disposed that its axis Y-Y, which in the position of rest is eccentric relative to the axis X-X, coincides with the latter in the armed position at Y -Y (FIGS. 7 and 8). It is hollowed out so as to receive a detonator and primer C of any known type which is ignited electrically, for example by a spark. In the presently-described embodiment, this primer and detonator C comprises a central electrode 17 and a peripheral electrode constituted by the case 18 of this primer. A dielectric 19 is provided between the two electrodes. The production of a spark between the two electrodes 17, 18 ignites the primer 2 and, through the latter, the charge 21 constituting a detonator, the flames emanating from the latter passing through an aperture 22 in the end of the case 18.

The third cylindrical portion 9 comprises a bore 23 having a shoulder 24 in which is movable in the direction of arrow f (FIG. 2) under the effect of inertia an auxiliary safety locking device 25 which a spring 26 tends to maintain in the position of rest shown in FIG. 2 in which this locking device is retracted from, but in alignment with, a locking cavity 27 formed in the inner face of the base 1 of the fuse body A, a split elastic ring 28 disposed in a peripheral recess 28a of the locking device being in this retracted position in abutment with the support B.

At rest, this support B is locked in the unarmed retracted position shown in FIGS. 1 to 3 by a locking device D which is automatically retracted by the effect of inertia, this retraction being delayed or retarded by a pneumatic dash-pot which is combined with a safety stopping device of utility in the event of a shock in the course of handling.

The device D comprises in combination: on the one hand, a heel 29 rigidly secured to the support B in such position that in the course of the pivoting of the support B for arming, this heel 29 in order to travel from the position shown in FIG. 1 to that shown in FIG. 7, must traverse in a direction perpendicular to the axis ZZ a cylindrical sleeve 30 which is maintained between the base 1 of the body A and the cover 3 in the bore of a boss 31 which is integral with the base 1 and is provided with an opening 32 for the free passage of the heel 29, and, on the other hand, a piston 33 which constitutes a locking device and is in its operative position, corresponding to the position of rest of the fuse, located (FIGS. 1 and 3) in the sleeve 30 in abutment, due to the action of a spring 34, against an elastic abutment ring 35 in such position that it blocks the opening 32 and thus the passage therethrough of the heel 29. The piston 33 is capable of sliding under the effect of inertia in opposition to the action of the spring 34 in the sleeve 30 and thus becoming retracted to the position shown in FIG. 8 so as to free the passage of the heel 29. It constitutes, moreover, the moving element of a braking dash-pot whose fixed element is constituted by the sleeve 30. The movement of the piston 33 toward the base 1 is braked or retarded by the necessity for the air contained in the space formed in the sleeve 30 and the piston 33 to escape through the small clearance between the inner face of the sleeve and the outer face of the piston or through a longitudinally extending groove of small section provided in the outer face of the piston. The braking or retarding action thus obtained can be so chosen that the movement of piston from the operative locking position shown in FIG. 3 to the retracted position shown in FIG. 8 requires some tenths of a second.

In order to preclude any undesired displacement owing to a shock in the course of handling, the piston 33 carries a lug or pin 36 which is adapted to move in the known manner in a zigzag groove 37 (FIGS. 3, 6 and 8) provided in the outer face of a cylindrical tube 38 attached by a flange 39 between the base 1 of the body A and a rebate in the sleeve 30. The groove 37 terminates in a projection or hump 39 (FIG. 6) which locks the lug 36 in the position corresponding to a retracted piston 33 (FIG. 8).

The assembly just described is completed by electric supply means supplying current to the primer and detonator, these means permitting in particular its connection to a piezo electric percussion fuse of known type (not shown in the drawings) disposed in the point of the projectile and adapted to operate on impact. These connecting means comprise two supply conductors 40 and 41. They are connected to the base fuse according to the invention in the following manner:

The conductors 40, 41 extend alongside the tube 2 and through the base 1 of the body A by way of an aperture 42 and are connected to the terminals 44 and 43 respectively (FIG. 5

The terminal 43 is fixed by a nut 45 (FIGS. 3 and 8) to the journal 11 of the primer and detonator support B and is permanently connected by way of this metal journal to the electrically conductive cover 3. Fixed to the latter by a screw 46 is a contact member 47 (FIGS. 1 and 7). This member is permanently connected by a floating conductor 48 in an insulating sheath to a stud 49 carried by the support B and is in permanent contact With the central electrode 17 (FIG. 2). Further, the contact member 47 is provided with a tab 50 with which comes into contact in the position of rest in an elastic manner a movable contact element 51 which participates in the pivotal motion of the support B to which latter it is connected, since it is wound round the cylindrical portion 9 of this support. The element 51 is in contact with the forward end of the case 18 constituting the outer electrode of the primer-detonator C and comprises an aperture 52 in alignment with the aperture 22' in this case. In the position of rest, the two electrodes 17 and 18 are therefore connected to the same conductor 40 respectively by the conductor 48 and the contact element 51 which are then both connected to the contact member 47, 50 (see FIGS. 1, 2 and 9).

The other terminal 44 (FIGS. 4 and 5) is connected by a screw 54 and a metal bushing 55 carried by the base 1 of the body A, to a contact member 56 located in the tube 2 against the inner face of the latter in such position that the movable element 51 comes into contact, by way of its part wound round the cylindrical portion 9 of the support B, when the latter is in the operative position (FIGS. 7 and 8), thereby achieving the connection of the electrode 18 and of the second conductor 41 by the element 51 and member 56 (FIG. 10).

The fuse according to the invention operates in the following manner:

At rest, the primer and detonator carrying support B is in the position shown in FIGS. 1, 2 and 3, the axis of the primer-detonator C is offset at YY relative to the axial hole 6 and the pyrotechnic chain is broken or interrupted. The metal cover 3 prevents the transmission of the flames of the detonator in the event of an undesired operation of the primer-detonator C.

The support B tends to pivot about the axis WW under the effect of the torsion spring 16 toward its operative position (the pyrotechnicchain or line being closed) shown in FIGS. 7 and 8 but this movement is prevented by the piston 33 against which the heel 29 of the support B bears.

When the rocket is launched, under the effect of the thrust imparted by the propelling means of the rocket, the piston 33 is shifted by the effect of inertia, compresses the spring 34 (FIG. 8) and releases the support B. However, any undesired arming of the fuse in the event of an accidental shock is prevented by the sleeve 38 owing to its zigzag groove 37 (FIGS. 3, 6 and 8) in which is engaged the lug 36 rigid with the piston 33. As is known, in the event of an accidental shock this lug 36 abuts against the zigzag walls and prevents any movement of the piston. On the other hand, in the course of the normal launching of the projectile, the lug 36 moves normally without shocks through the groove 37, the piston 33 turning round the axis ZZ in the sleeve 30, and the lug reaches the end of the zig-zag groove and becomes hooked there by the projection 39 (FIG. 8) and thus prevents the piston 33 from moving forwardly.

The retraction of the piston 33 is retarded by the dashpot constituted by this piston and its mounting in the sleeve 30. In this way, there is obtained a delay in the unlocking of the support B of some tenths of a second, so that if the rocket becomes accidentally wedged in its launching tube the support B remains locked and the fuse remains unarmed.

There is also obtained in the same way safe operation as concerns a possible explosion of the projectile near the muzzle of the launching tube, in other words, the fuse is only armed at the end of a given travel corresponding to the delay in the unlocking of the support B (assuming that the spring 16 ensuring the pivotal motion of the support B has such strength as to overcome the friction of the support B against the inner face of the base 1 due to inertia throughout the duration of the thrust exerted by the propelling means of the rocket).

Furthermore, the annular safety locking device 25 (FIG. 6) which is biased toward its position of rest by the spring 26 and whose end is engaged by the effect of inertia during the thrust of the propelling means in the opening 1 holds the support B stationary in its safety position until the end of the acceleration of the rocket, that is, until the end of its propulsion.

It should be noted that this safety locking device 25 alone would not be able to prevent in a sure manner the arming of the fuse in the event of a wedging of the rocket in its launching tube and this is the function of the device D and in particular the dash-pot.

From the electrical point of view, as the central electrode 17 is connected by means of the stud 49 and the insulated conductor 48 to the contact member 47 connected by the cover 3 to the conductor 40 and the electrode 18 is connected to the element 51 fixed to the support B and the latter comes into contact with the member 47 when the support B is in the state of rest, it is clear that, at rest, the two terminals of the primerdetonator C are short circuited (FIG. 9) and an undesired ignition cannot take place.

In the armed position, on the other hand, the electrodes 17 and 18 of the primer-detonator C are respectively connected to the conductors 4th and 41, and if the conductors are connected, for example, to the terminals of a piezoelectric fuse of any known type disposed in the nose of the rocket, on impact the electric fuse, which is then armed, is supplied with current and thereafter ignited. As its vprimer-detonator C is then in alignment with the aperture 6 in the cover 3 the pyrotechnic chain is achieved and the charge of the rocket is ignited.

FIG. 11 shows very diagrammatically a rocket R comprising the piezo-electric fuse F the hollow charge E, the electric fuse F according to the invention with its conductors 40, 41, the propelling charge P and the nozzle T for the ejection of the propelling gases.

Although specific embodiments of the invention have been described, many modifications and changes may be made therein without departing from the scope of the invention as defined in the appended claims.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. In an electric fuse of utility in a non-gyratory projectile having an explosive charge and electric current producing means, the fuse having a body and, disposed within the body, a pivotal support and an electric primerdetonator carried by the support the primer-detonator having two primer-igniting electrodes carried by the support, a spring interposed between the support and the body for biasing the support in a direction from an unarmed fuse position in which the primer-detonator is in misalignment with the explosive charge to an armed fuse position in which the primer-detonator is in alignment with the explosive charge; the structure comprising, in combination with the support, a dashpot device mounted in the body and having a chamber, a damping fluid in the chamber and a member movable relative to the chamber, by the effect of inertia when the projectile accelerates, in opposition to the retarding action of the damping fluid, between a retaining position in which said member directly engages and retains the support in said unarmed fuse position and a retracted position in which said member disengages from and releases the support and allows the support to pivot to said armed fuse position, and an electric switching means for connecting said electric current producing means to said electric primer-detonator, the switching means comprising a first terminal and a second terminal mounted on the body, said current producing means having a first conductor connected to the first terminal and a second conductor connected to the second terminal, the first terminal being permanently connected to one of the electrodes of the primer-detonator, a contact member mounted on the support and permanently connected to the other electrode of the primer-detonator, the contact member being in contact with said first terminal in said unarmed fuse position of the support thereby short-circuiting the primer-detonator and being disconnected from the first terminal and connected to the second terminal in said armed fuse position of the support.

2. An electric fuse as claimed in claim 1 wherein said dashpot device comprises a piston constituting said movable member and a cylinder in which the piston is movable and forms with the cylinder said chamber, said damping fluid being air and the volume of the chamber being reduced when the piston moves under the effect of inertia when the projectile accelerates, a small passageway being provided between the piston and cylinder to allow said air to escape at a predetermined rate in accordance with the delay desired in the release of the support, and a spring interposed between the piston and the cylinder for biasing the piston in the di rection opposed to the direction in which the piston moves under the effect of inertia when the projectile accelerates.

3. An electric fuse as claimed in claim 2, further comprising means defining a zig-zag groove which is rigid with said cylinder and has a first end and a second end, and a pin rigid with said piston and engaged in the first end of the zigzag groove in said retaining position of the piston, the second end of the zigzag groove comprising a notch in which the pin in the piston engages and becomes locked when the piston reaches said retracted position so as to lock the piston in said retracted position.

4. In an electric fuse of utility in a non-gyratory projectile having an explosive charge and a piezoelectric fuse, the fuse having a body and, disposed within the body, a pivotal support and an electric primer-detonator carried by the support, the primer-detonator having two primer-igniting electrodes carried by the support, a spring interposed between the body and the support for biasing the support in a direction from an unarmed fuse position in which the primer-detonator is in misalignment with the explosive charge to an armed fuse position in which the primer-detonator is in alignment with the explosive charge; the structure comprising, in combination with the support, a dashpot device mounted in the body and having a chamber, a damping fluid in the chamber and a member movable relative to the chamber, by the effect of inertia when the projectile accelerates, in opposition to the retarding action of the damping fluid, between a retaining position in which said member directly engages and retains the support in said unarmed fuse position and a retracted position in which said member disengages from and releases the support and allows the support to pivot to said armed fuse position, and an electric switching means for connecting the piezo-electric fuse to said electric primer-detonator, the swtiching means comprising a first terminal and a second terminal mounted on the body and the piezoelectric fuse having a first conductor connected to said first terminal and a second conductor connected to said second terminal, the first terminal being permanently connected to one of the electrodes of the primer-detonator, a contact member mounted on the support and permanently connected to the other electrode of the primerdetonator, the contact member being in contact with said first terminal in said unarmed fuse position of the support thereby short-circuiting the primer-detonator and being disconnected from the first terminal and connected to the second terminal in said armed fuse position of the support.

5. In an electric fuse of utility in a non-gyratory projectile having an explosive charge and electric current producing means, the fuse being of the type having a body and, disposed within the body, a pivotal support and an electric primer-detonator carried by the support, the primer-detonator having two primer-igniting electrodes carried by the support, a spring interposed between the body and the support for biasing the support in a direction from an unarmed fuse position in which the primer-detonator is in misalignment with the explosive charge to an armed fuse position in which the primer-detonator is in alignment with the explosive charge; the structure comprising, in combination with the support, a dashpot device mounted in the body and having a chamber, a damping fluid in the chamber and a member movable relative to the chamber in oppositon to the retarding action of the damping fluid, between a retaining position in which said member directly engages and retains the support in said unarmed fuse position and a retracted position in which said member disengages from and releases the support and allows the support to pivot to said armed fuse position, an electric switching means for connecting said electric current producing means to said electric primer-detonator, the switching means comprising a first terminal and a second terminal mounted on the body, said electric current producing means having a first conductor connected to the first terminal and a second conductor connected to the second terminal, the first terminal being permanently connected to one of the electrodes of the primerdetonator, a contact member mounted on the support and permanently connected to the other electrode of the primer-detonator, the contact member being in contact with said first terminal in said unarmed fuse position of the support thereby short-circuiting the primerdetonator and being disconnected from the first terminal and connected to the second terminal in said armed fuse position of the support, and an auxiliary locking References Cited in the file of this patent UNITED STATES PATENTS 2,853,011 Will et a1. Sept. 23, 1958 2,934,019 Olsen Apr. 26, 1960 2,975,711 Brown et al Mar. 21, 1961 2,994,271 Silver et al. Aug. 1, 1961 3,000,313 Lareau et al. Sept. 19, 1961 

1. IN AN ELECTRIC FUSE OF UTILITY IN A NON-GYRATORY PROJECTILE HAVING AN EXPLOSIVE CHARGE AND ELECTRIC CURRENT PRODUCING MEANS, THE FUSE HAVING A BODY AND, DISPOSED WITHIN THE BODY, A PIVOTAL SUPPORT AND AN ELECTRIC PRIMERDETONATOR CARRIED BY THE SUPPORT THE PRIMER-DETONATOR HAVING TWO PRIMER-IGNITING ELECTRODES CARRIED BY THE SUPPORT, A SPRING INTERPOSED BETWEEN THE SUPPORT AND THE BODY FOR BIASING THE SUPPORT IN A DIRECTION FROM AN UNARMED FUSE POSITION IN WHICH THE PRIMER-DETONATOR IS IN MISALIGNMENT WITH THE EXPLOSIVE CHARGE TO AN ARMED FUSE POSITION IN WHICH THE PRIMER-DETONATOR IS IN ALIGNMENT WITH THE EXPLOSIVE CHARGE; THE STRUCTURE COMPRISING, IN COMBINATION WITH THE SUPPORT, A DASHPOT DEVICE MOUNTED IN THE BODY AND HAVING A CHAMBER, A DAMPING FLUID IN THE CHAMBER AND A MEMBER MOVABLE RELATIVE TO THE CHAMBER, BY THE EFFECT OF INERTIA WHEN THE PROJECTILE ACCELERATES, IN OPPOSITION TO THE RETARDING ACTION OF THE DAMPING FLUID, BETWEEN A RETAINING POSITION IN WHICH SAID MEMBER DIRECTLY ENGAGES AND RETAINS THE SUPPORT IN SAID UNARMED FUSE POSITION AND A RETRACTED POSITION IN WHICH SAID MEMBER DISENGAGES FROM AND RELEASES THE SUPPORT AND ALLOWS THE SUPPORT TO PIVOT TO SAID ARMED FUSE POSITION, AND AN ELECTRIC SWITCHING MEANS FOR CONNECTING SAID ELECTRIC CURRENT PRODUCING MEANS TO SAID ELECTRIC PRIMER-DETONATOR, THE SWITCHING MEANS COMPRISING A FIRST TERMINAL AND A SECOND TERMINAL MOUNTED ON THE BODY, SAID CURRENT PRODUCING MEANS HAVING A FIRST CONDUCTOR CONNECTED TO THE FIRST TERMINAL AND A SECOND CONDUCTOR CONNECTED TO THE SECOND TERMINAL, THE FIRST TERMINAL BEING PERMANENTLY CONNECTED TO ONE OF THE ELECTRODES OF THE PRIMER-DETONATOR, A CONTACT MEMBER MOUNTED ON THE SUPPORT AND PERMANENTLY CONNECTED TO THE OTHER ELECTRODE OF THE PRIMER-DETONATOR, THE CONTACT MEMBER BEING IN CONTACT WITH SAID FIRST TERMINAL IN SAID UNARMED FUSE POSITION OF THE SUPPORT THEREBY SHORT-CIRCUITING THE PRIMER-DETONATOR AND BEING DISCONNECTED FROM THE FIRST TERMINAL AND CONNECTED TO THE SECOND TERMINAL IN SAID ARMED FUSE POSITION OF THE SUPPORT. 